expression
outrageous; scandalous; inexcusable; shameful; rude
A strong, somewhat old-fashioned expression of moral indignation. Often used when someone's behavior is beyond acceptable limits. The form けしからん is a variant.
See also: 怪しからん
そんなことを言うとはけしからん。
It is outrageous to say such a thing.
彼の態度はまったくけしからぬ。
His attitude is absolutely inexcusable.